Activation in two or three dimensional arrays of actuators, particularly where the actuators affect a surface shape over a quasi-continuum, have not been developed to date, even though localized and global shape control of relatively large surfaces would offer significant advantage in various technologies. Examples of these technologies where a significant need exists are, among others, micro adaptive flow control, flight control in micro UAV, acoustics, and drag control.
In order to accomplish the yet to be developed control of surfaces, an actuation principle that allows the actuation of large surfaces with out-of-plane forces is desirable. If there is to be adequate control of small flying objects, simple, light, low power actuators are mandatory. Various actuation devices which affect a surface are known to have drawbacks which prevent their use broadly and certainly limit their use in the various needs described above.
Electromagnetic actuation requires heavy magnetic materials and relatively large currents, and the construction of such devices is not compact enough to be suitable for actuation of large surfaces. Clearly, for flight applications this method is excluded because of poor power/weight performance.
Electrothermally induced actuation is structurally suited for activator arrays, but also has the drawbacks of high power requirements, low speed of response and, in many cases dependence on environmental temperatures. Similarly, piezoelectric actuation, while structurally fitted for actuator arrays and uses low power with adequate or high speed, does not possess the displacements needed and are, in fact, so low as to not be useful for the above considered applications. Piezoelectric materials with increased performance have been proposed, but are both very expensive and heavier than would be acceptable.
It would be of great advantage to the art if a low weight, low power, high performance actuator could be developed which would permit localized and global shape control of relatively large surfaces.
It would be another great advance in the art if actuator arrays could be designed which would permit construction of large two and three dimensional arrays useful in a wide range of applications in flow and sound propagation control.
Other advantages will appear hereinafter.